Solar panels for your car

Japanese newspaper Nikkei reported on a rumor last week that next years’ Toyota Prius model will boast even more fuel efficiency, thanks to a set of rooftop solar panels. Toyota won’t comment either way – but this got Technology Review asking, “Does car-mounted solar make sense?”

More than a decade ago, Mazda souped up its 929 luxury sedan with solar cells embedded into the sunroof. The optional feature powered small fans that ventilated the car while it was parked in the sun. Not a bad idea. But like most of the car-mounted panels that followed Mazda’s design, the cost never quite matched the usefulness.

“Most onboard solar systems to date have cost several thousand dollars while generating less than 100 watts of energy, [enough to power a single light bulb]," reports Technology Review. That much energy improves “a vehicle’s fuel efficiency by just a few percent.”

While not much of a kick, it could push the plug-in from 100 miles per gallon to 105. But is that 5 percent boost worth the extra $3,500? If Toyota does plan to install sun-soaking cells in its next Prius, maybe it can negotiate a lower price. Or perhaps Toyota is sitting on a solar technology that has yet to hit the market.

For now, says NREL, a better option is to forget about a rooftop panel and invest in stationary solar cells. Park the car and plug it in. While less imaginative, it avoids many of the problems that plague mobile arrays. Right now, car-mounted units don’t tilt to face the sun, meaning they often do not absorb as many rays as possible. Another problem: you can only fit so many solar cells on to a single car roof.

But even if sun-powered cars sound better to an automaker’s marketing department than to its engineering crew, the pitch could get more consumers thinking about a post-petroleum future. “Whether it’s perception or real doesn’t matter,” says UC-Davis professor Andrew Frank, “because it creates public awareness.”